Interference cancellation in a spread spectrum communication system

ABSTRACT

A method and apparatus used to transmit and receive weighted data transmissions over a plurality of antennas using a plurality of different pilot signals. Different pilot signals are produced and a different pilot signal of the plurality of pilot signals is transmitted on each of a plurality of antennas. Each of the pilot signals is derived from a pseudo noise (PN) sequence and a bit sequence of the PN sequence for each of the pilot signals is different. A plurality of data streams are produced in which each of the data streams has data bits combined with bits of a PN sequence. The data streams are weighted in response to weight information received from a receiving device and the plurality of weighted data streams are transmitted using the plurality of antennas.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/117,233 filed on May 27, 2011, which is a continuation of U.S. patentapplication Ser. No. 12/480,337 filed Jun. 8, 2009, now U.S. Pat. No.7,953,139 which issued on May 31, 2011, which is a continuation of U.S.patent application Ser. No. 11/301,666 filed Dec. 13, 2005, now U.S.Pat. No. 7,545,846 which issued on Jun. 9, 2009, which is a continuationof U.S. patent application Ser. No. 10/923,950, filed Aug. 23, 2004, nowU.S. Pat. No. 6,985,515 issued Jan. 10, 2006, which is a continuation ofSer. No. 10/423,230, filed Apr. 25, 2003, now U.S. Pat. No. 6,782,040issued Aug. 24, 2004, which is a continuation of Ser. No. 09/892,369filed Jun. 27, 2001, now U.S. Pat. No. 6,574,271 issued Jun. 3, 2003,which is a continuation of Ser. No. 09/659,858, filed on Sep. 11, 2000,now U.S. Pat. No. 6,278,726, issued on Aug. 21, 2001, which is acontinuation-in-part of Ser. No. 09/602,963 filed Jun. 23, 2000, nowU.S. Pat. No. 6,373,877, issued Apr. 16, 2002, which is a continuationof Ser. No. 09/394,452 filed Sep. 10, 1999, now U.S. Pat. No. 6,115,406,issued Sep. 5, 2000, which are incorporated by reference as if fully setforth.

FIELD OF INVENTION

The present invention relates generally to signal transmission andreception in a wireless code division multiple access (CDMA)communication system. More specifically, the invention relates toreception of signals to reduce interference in a wireless CDMAcommunication system.

BACKGROUND

A prior art CDMA communication system is shown in FIG. 1. Thecommunication system has a plurality of base stations 20-32. Each basestation 20 communicates using spread spectrum CDMA with user equipment(UEs) 34-38 within its operating area. Communications from the basestation 20 to each UE 34-38 are referred to as downlink communicationsand communications from each UE 34-38 to the base station 20 arereferred to as uplink communications.

Shown in FIG. 2 is a simplified CDMA transmitter and receiver. A datasignal having a given bandwidth is mixed by a mixer 40 with a pseudorandom chip code sequence producing a digital spread spectrum signal fortransmission by an antenna 42. Upon reception at an antenna 44, the datais reproduced after correlation at a mixer 46 with the same pseudorandom chip code sequence used to transmit the data. By using differentpseudo random chip code sequences, many data signals use the samechannel bandwidth. In particular, a base station 20 will communicatesignals to multiple UEs 34-38 over the same bandwidth.

For timing synchronization with a receiver, an unmodulated pilot signalis used. The pilot signal allows respective receivers to synchronizewith a given transmitter allowing despreading of a data signal at thereceiver. In a typical CDMA system, each base station 20 sends a uniquepilot signal received by all UEs 34-38 within communicating range tosynchronize forward link transmissions. Conversely, in some CDMAsystems, for example in the B-CDMA™ air interface, each UE 34-38transmits a unique assigned pilot signal to synchronize reverse linktransmissions.

When a UE 34-38 or a base station 20-32 is receiving a specific signal,all the other signals within the same bandwidth are noise-like inrelation to the specific signal. Increasing the power level of onesignal degrades all other signals within the same bandwidth. However,reducing the power level too far results in an undesirable receivedsignal quality. One indicator used to measure the received signalquality is the signal to noise ratio (SNR). At the receiver, themagnitude of the desired received signal is compared to the magnitude ofthe received noise. The data within a transmitted signal received with ahigh SNR is readily recovered at the receiver. A low SNR leads to lossof data.

To maintain a desired signal to noise ratio at the minimum transmissionpower level, most CDMA systems utilize some form of adaptive powercontrol. By minimizing the transmission power, the noise between signalswithin the same bandwidth is reduced. Accordingly, the maximum number ofsignals received at the desired signal to noise ratio within the samebandwidth is increased.

Although adaptive power control reduces interference between signals inthe same bandwidth, interference still exists limiting the capacity ofthe system. One technique for increasing the number of signals using thesame radio frequency (RF) spectrum is to use sectorization. Insectorization, a base station uses directional antennas to divide thebase station's operating area into a number of sectors. As a result,interference between signals in differing sectors is reduced. However,signals within the same bandwidth within the same sector interfere withone another. Additionally, sectorized base stations commonly assigndifferent frequencies to adjoining sectors decreasing the spectralefficiency for a given frequency bandwidth. Accordingly, there exists aneed for a system which further improves the signal quality of receivedsignals without increasing transmitter power levels.

SUMMARY

A method and apparatus used to transmit and receive weighted datatransmissions over a plurality of antennas using a plurality ofdifferent pilot signals. Different pilot signals are produced and adifferent pilot signal of the plurality of pilot signals is transmittedon each of a plurality of antennas. Each of the pilot signals is derivedfrom a pseudo noise (PN) sequence and a bit sequence of the PN sequencefor each of the pilot signals is different. A plurality of data streamsare produced in which each of the data streams has data bits combinedwith bits of a PN sequence. The data streams are weighted in response toweight information received from a receiving device and the plurality ofweighted data streams are transmitted using the plurality of antennas.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a prior art wireless spread spectrum CDMA communicationsystem.

FIG. 2 is a prior art spread spectrum CDMA transmitter and receiver.

FIG. 3 is the transmitter of the invention.

FIG. 4 is the transmitter of the invention transmitting multiple datasignals.

FIG. 5 is the pilot signal receiving circuit of the invention.

FIG. 6 is the data signal receiving circuit of the invention.

FIG. 7 is an embodiment of the pilot signal receiving circuit.

FIG. 8 is a least mean squared weighting circuit.

FIG. 9 is the data signal receiving circuit used with the pilot signalreceiving circuit of FIG. 7.

FIG. 10 is an embodiment of the pilot signal receiving circuit where theoutput of each RAKE is weighted.

FIG. 11 is the data signal receiving circuit used with the pilot signalreceiving circuit of FIG. 10.

FIG. 12 is an embodiment of the pilot signal receiving circuit where theantennas of the transmitting array are closely spaced.

FIG. 13 is the data signal receiving circuit used with the pilot signalreceiving circuit of FIG. 12.

FIG. 14 is an illustration of beam steering in a CDMA communicationsystem.

FIG. 15 is a beam steering transmitter.

FIG. 16 is a beam steering transmitter transmitting multiple datasignals.

FIG. 17 is the data receiving circuit used with the transmitter of FIG.14.

FIG. 18 is a pilot signal receiving circuit used when uplink anddownlink signals use the same frequency.

FIG. 19 is a transmitting circuit used with the pilot signal receivingcircuit of FIG. 18.

FIG. 20 is a data signal receiving circuit used with the pilot signalreceiving circuit of FIG. 18.

FIG. 21 is a simplified receiver for reducing interference.

FIG. 22 is an illustration of a vector correlator/adaptive algorithmblock using a least mean square error algorithm.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

The preferred embodiments will be described with reference to thedrawing figures where like numerals represent like elements throughout.FIG. 3 is a transmitter of the invention. The transmitter has an arrayof antennas 48-52, preferably 3 or 4 antennas. For use in distinguishingeach antenna 48-52, a different signal is associated with each antenna56-60. The preferred signal to associate with each antenna is a pilotsignal as shown in FIG. 3. Each spread pilot signal is generated by apilot signal generator 56-60 using a different pseudo random chip codesequence and is combined by combiners 62-66 with the respective spreaddata signal. Each spread data signal is generated using data signalgenerator 54 by mixing at mixers 378-382 the generated data signal witha different pseudo random chip code sequence per antenna 48-52,D₁-D_(N). The combined signals are modulated to a desired carrierfrequency and radiated through the antennas 48-52 of the array.

By using an antenna array, the transmitter utilizes spacial diversity.If spaced far enough apart, the signals radiated by each antenna 48-52will experience different multipath distortion while traveling to agiven receiver. Since each signal sent by an antenna 48-52 will followmultiple paths to a given receiver, each received signal will have manymultipath components. These components create a virtual communicationchannel between each antenna 48-52 of the transmitter and the receiver.Effectively, when signals transmitted by one antenna 48-52 over avirtual channel to a given receiver are fading, signals from the otherantennas 48-52 are used to maintain a high received SNR. This effect isachieved by the adaptive combining of the transmitted signals at thereceiver.

FIG. 4 shows the transmitter as used in a base station 20 to sendmultiple data signals. Each spread data signal is generated by mixing atmixers 360-376 a corresponding data signal from generators 74-78 withdiffering pseudo random chip code sequences D₁₁-D_(NM). Accordingly,each data signal is spread using a different pseudo random chip codesequence per antenna 48-52, totaling N×M code sequences. N is the numberof antennas and M is the number of data signals. Subsequently, eachspread data signal is combined with the spread pilot signal associatedwith the antenna 48-52. The combined signals are modulated and radiatedby the antennas 48-52 of the array.

The pilot signal receiving circuit is shown in FIG. 5. Each of thetransmitted pilot signals is received by the antenna 80. For each pilotsignal, a despreading device, such as a RAKE 82-86 as shown in the FIG.5 or a vector correlator, is used to despread each pilot signal using areplica of the corresponding pilot signal's pseudo random chip codesequence. The despreading device also compensates for multipath in thecommunication channel. Each of the recovered pilot signals is weightedby a weighting device 88-92. Weight refers to both magnitude and phaseof the signal. Although the weighting is shown as being coupled to aRAKE, the weighting device preferably also weights each finger of theRAKE. After weighting, all of the weighted recovered pilot signals arecombined in a combiner 94. Using an error signal generator 98, anestimate of the pilot signal provided by the weighted combination isused to create an error signal. Based on the error signal, the weightsof each weighting device 88-92 are adjusted to minimize the error signalusing an adaptive algorithm, such as least mean squared (LMS) orrecursive least squares (RLS). As a result, the signal quality of thecombined signal is maximized.

FIG. 6 depicts a data signal receiving circuit using the weightsdetermined by the pilot signal recovery circuit. The transmitted datasignal is recovered by the antenna 80. For each antenna 48-52 of thetransmitting array, the weights from a corresponding despreading device,shown as a RAKE 82-86, are used to filter the data signal using areplica of the data signal's spreading code used for the correspondingtransmitting antenna. Using the determined weights for each antenna'spilot signal, each weighting device 106-110 weights the RAKE's despreadsignal with the weight associated with the corresponding pilot. Forinstance, the weighting device 88 corresponds to the transmittingantenna 48 for pilot signal 1. The weight determined by the pilot RAKE82 for pilot signal 1 is also applied at the weighting device 106 ofFIG. 6. Additionally, if the weights of the RAKE's fingers were adjustedfor the corresponding pilots signal's RAKE 82-86, the same weights willbe applied to the fingers of the data signal's RAKE 100-104. Afterweighting, the weighted signals are combined by the combiner 112 torecover the original data signal.

By using the same weights for the data signal as used with eachantenna's pilot signal, each RAKE 82-86 compensates for the channeldistortion experienced by each antenna's signals. As a result, the datasignal receiving circuit optimizes the data signal's reception over eachvirtual channel. By optimally combining each virtual channel's optimizedsignal, the received data signal's signal quality is increased.

FIG. 7 shows an embodiment of the pilot signal recovery circuit. Each ofthe transmitted pilots are recovered by the receiver's antenna 80. Todespread each of the pilots, each RAKE 82-86 utilizes a replica of thecorresponding pilot's pseudo random chip code sequence, P₁-P_(N).Delayed versions of each pilot signal are produced by delay devices114-124. Each delayed version is mixed by a mixer 126-142 with thereceived signal. The mixed signals pass through sum and dump circuits424-440 and are weighted using mixers 144-160 by an amount determined bythe weight adjustment device 170. The weighted multipath components foreach pilot are combined by a combiner 162-164. Each pilot's combinedoutput is combined by a combiner 94. Since a pilot signal has no data,the combined pilot signal should have a value of 1+j0. The combinedpilot signal is compared to the ideal value, 1+j0, at a subtractor 168.Based on the deviation of the combined pilot signal from the ideal, theweight of the weighting devices 144-160 are adjusted using an adaptivealgorithm by the weight adjustment device 170.

An LMS algorithm used for generating a weight is shown in FIG. 8. Theoutput of the subtractor 168 is multiplied using a mixer 172 with thecorresponding despread delayed version of the pilot. The multipliedresult is amplified by an amplifier 174 and integrated by an integrator176. The integrated result is used to weight, W_(1M), the RAKE finger.

The data receiving circuit used with the embodiment of FIG. 7 is shownfor a base station receiver in FIG. 9. The received signal is sent to aset of RAKEs 100-104 respectively associated with each antenna 48-52 ofthe array. Each RAKE 100-104, produces delayed versions of the receivedsignal using delay devices 178-188. The delayed versions are weightedusing mixers 190-206 based on the weights determined for thecorresponding antenna's pilot signal. The weighted data signals for agiven RAKE 100-104 are combined by a combiner 208-212. One combiner208-212 is associated with each of the N transmitting antennas 48-52.Each combined signal is despread M times by mixing at a mixer 214-230the combined signal with a replica of the spreading codes used forproducing the M spread data signals at the transmitter, D₁₁-D_(NM). Eachdespread data signal passes through a sum and dump circuit 232-248. Foreach data signal, the results of the corresponding sum and dump circuitsare combined by a combiner 250-254 to recover each data signal.

Another pilot signal receiving circuit is shown in FIG. 10. Thedespreading circuits 82-86 of this receiving circuit are the same asFIG. 7. The output of each RAKE 82-86 is weighted using a mixer 256-260prior to combining the despread pilot signals. After combining, thecombined pilot signal is compared to the ideal value and the result ofthe comparison is used to adjust the weight of each RAKE's output usingan adaptive algorithm. To adjust the weights within each RAKE 82-86, theoutput of each RAKE 82-86 is compared to the ideal value using asubtractor 262-266. Based on the result of the comparison, the weight ofeach weighting device 144-160 is determined by the weight adjustmentdevices 268-272.

The data signal receiving circuit used with the embodiment of FIG. 10 isshown in FIG. 11. This circuit is similar to the data signal receivingcircuit of FIG. 9 with the addition of mixers 274-290 for weighting theoutput of each sum and dump circuit 232-248. The output of each sum anddump circuit 232-248 is weighted by the same amount as the correspondingpilot's RAKE 82-86 was weighted. Alternatively, the output of eachRAKE's combiner 208-212 may be weighted prior to mixing by the mixers214-230 by the amount of the corresponding pilot's RAKE 82-86 in lieu ofweighting after mixing.

If the spacing of the antennas 48-52 in the transmitting array is small,each antenna's signals will experience a similar multipath environment.In such cases, the pilot receiving circuit of FIG. 12 may be utilized.The weights for a selected one of the pilot signals are determined inthe same manner as in FIG. 10. However, since each pilot travels throughthe same virtual channel, to simplify the circuit, the same weights areused for despreading the other pilot signals. Delay devices 292-294produce delayed versions of the received signal. Each delayed version isweighted by a mixer 296-300 by the same weight as the correspondingdelayed version of the selected pilot signal was weighted. The outputsof the weighting devices are combined by a combiner 302. The combinedsignal is despread using replicas of the pilot signals' pseudo randomchip code sequences, P₂-P_(n), by the mixers 304-306. The output of eachpilot's mixer 304-306 is passed through a sum and dump circuit 308-310.In the same manner as FIG. 10, each despread pilot is weighted andcombined.

The data signal recovery circuit used with the embodiment of FIG. 12 isshown in FIG. 13. Delay devices 178-180 produce delayed versions of thereceived signal. Each delayed version is weighted using a mixer 190-194by the same weight as used by the pilot signals in FIG. 12. The outputsof the mixers are combined by a combiner 208. The output of the combiner208 is inputted to each data signal despreader of FIG. 13.

The invention also provides a technique for adaptive beam steering asillustrated in FIG. 14. Each signal sent by the antenna array willconstructively and destructively interfere in a pattern based on theweights provided each antenna 48-52 of the array. As a result, byselecting the appropriate weights, the beam 312-316 of the antenna arrayis directed in a desired direction.

FIG. 15 shows the beam steering transmitting circuit. The circuit issimilar to the circuit of FIG. 3 with the addition of weighting devices318-322. A target receiver will receive the pilot signals transmitted bythe array. Using the pilot signal receiving circuit of FIG. 5, thetarget receiver determines the weights for adjusting the output of eachpilot's RAKE. These weights are also sent to the transmitter, such as byusing a signaling channel. These weights are applied to the spread datasignal as shown in FIG. 15. For each antenna, the spread data signal isgiven a weight by the weighting devices 318-322 corresponding to theweight used for adjusting the antenna's pilot signal at the targetreceiver providing spatial gain. As a result, the radiated data signalwill be focused towards the target receiver. FIG. 16 shows the beamsteering transmitter as used in a base station sending multiple datasignals to differing target receivers. The weights received by thetarget receiver are applied to the corresponding data signals byweighting devices 324-340.

FIG. 17 depicts the data signal receiving circuit for the beam steeringtransmitter of FIGS. 15 and 16. Since the transmitted signal has alreadybeen weighted, the data signal receiving circuit does not require theweighting devices 106-110 of FIG. 6.

The advantage of the invention's beam steering is two-fold. Thetransmitted data signal is focused toward the target receiver improvingthe signal quality of the received signal. Conversely, the signal isfocused away from other receivers reducing interference to theirsignals. Due to both of these factors, the capacity of a system usingthe invention's beam steering is increased. Additionally, due to theadaptive algorithm used by the pilot signal receiving circuitry, theweights are dynamically adjusted. By adjusting the weights, a datasignal's beam will dynamically respond to a moving receiver ortransmitter as well as to changes in the multipath environment.

In a system using the same frequency for downlink and uplink signals,such as time division duplex (TDD), an alternate embodiment is used. Dueto reciprocity, downlink signals experience the same multipathenvironment as uplink signals sent over the same frequency. To takeadvantage of reciprocity, the weights determined by the base station'sreceiver are applied to the base station's transmitter. In such asystem, the base station's receiving circuit of FIG. 18 is co-located,such as within a base station, with the transmitting circuit of FIG. 19.

In the receiving circuit of FIG. 18, each antenna 48-52 receives arespective pilot signal sent by the UE. Each pilot is filtered by a RAKE406-410 and weighted by a weighting device 412-416. The weighted andfiltered pilot signals are combined by a combiner 418. Using the errorsignal generator 420 and the weight adjustment device 422, the weightsassociated with the weighting devices 412-416 are adjusted using anadaptive algorithm.

The transmitting circuit of FIG. 19 has a data signal generator 342 togenerate a data signal. The data signal is spread using mixer 384. Thespread data signal is weighted by weighting devices 344-348 as weredetermined by the receiving circuit of FIG. 19 for each virtual channel.

The circuit of FIG. 20 is used as a data signal receiving circuit at thebase station. The transmitted data signal is received by the multipleantennas 48-52. A data RAKE 392-396 is coupled to each antenna 48-52 tofilter the data signal. The filtered data signals are weighted byweighting devices 398-402 by the weights determined for thecorresponding antenna's received pilot and are combined at combiner 404to recover the data signal. Since the transmitter circuit of FIG. 19transmits the data signal with the optimum weights, the recovered datasignal at the UE will have a higher signal quality than provided by theprior art.

An adaptive algorithm can also be used to reduce interference inreceived signals for a spread spectrum communication system. Atransmitter in the communication system, which can be located in eithera base station 20 to 32 or UE 34 to 36, transmits a spread pilot signaland a traffic signal over the same frequency spectrum. The pilot signalis spread using a pilot code, P, and the traffic signal is spread usinga traffic code, C.

The simplified receiver 500 of FIG. 21 receives both the pilot andtraffic signals using an antenna 502. The received signals aredemodulated to a baseband signal by a demodulator 518. The basebandsignal is converted into digital samples, such as by two analog todigital converters (ADC) 512, 514. Each ADC 512, 514 typically samplesat the chip rate. To obtain a half-chip resolution, one ADC 514 isdelayed with respect to the other ADC 512 by a one-half chip delay. Thesamples are processed by a filtering device, such two vector correlators504, 508 as shown in FIG. 21 or a RAKE, to process the pilot signal. Thevector correlators 504, 508, are used to despread various multipathcomponents of the received pilot signal using the pilot code, P. Byusing two vector correlators 504, 508 as in FIG. 21, each half-chipcomponent is despread, such as for a 10 chip window to despread 21components. Each despread component is sent to an adaptive algorithmblock 506 to determine an optimum weight for each despread component tominimize interference in the received pilot signal. The adaptivealgorithm block 506 may use a minimum mean square error (MMSE) algorithmsuch as a least mean square error algorithm.

One combination vector correlator/adaptive algorithm block using an LMSalgorithm and half-chip resolution is shown in FIG. 22. The pilot codeis delayed by a group of delay devices 5201 to 520N and 5221 to 522N.Each of the ADC samples is despread such as by mixing it with timedversions of the pilot code, P, by mixers 5241 to 524N and 5261 to 526N.The mixed signals are processed by sum and dump circuits 5281 to 528Nand 5301 to 530N to produce despread components of the pilot signal. Byusing two ADCs 512, 514 with a half-chip sampling delay and two vectorcorrelators 504, 508, despread components at half-chip intervals areproduced such as 21 components for a 10 chip window. Each despreadversion is weighted by a weight, W₁₁ to W_(2N), such as by using aweighting device, 544 ₁ to 544 _(N) and 546 ₁ to 546 _(N). The weightedversions are combined, such as by using a summer 528. The combinedsignal is compared to the complex transmitted value of pilot signal,such as 1+j for a pilot signal in the third generation wirelessstandard, to produce an error signal, e. The comparison may be performedby a subtractor 550 by subtracting the combined signal from the ideal,1+j. The error signal, e, is mixed using mixers 532 ₁ to 532 _(N) and534 ₁ to 534 _(N) with each despread version. Each mixed version isamplified and integrated, such as by using an amplifier 536 ₁ to 536_(N) and 538 ₁ to 538 _(N) and an integrator 540 ₁ to 540 _(N) and 542 ₁to 542 _(N). The amplified and integrated results are refined weights,W₁₁ to W_(2N), for further weighting of the despread versions. Using theleast mean square algorithm, the weights, W₁₁ to W_(2N), will beselected as to drive the combined signal to its ideal value.

The received signal is also processed by an adaptive filter 510 with theweights, W₁₁ to W_(2N), determined for the pilot signal components.Since the pilot signal and the traffic signal are transmitted over thesame frequency spectrum, the two signals experience the same channelcharacteristics. As a result, the pilot weights, W₁₁ to W_(2N), appliedto the traffic signal components reduces interference in the receivedtraffic signal. Additionally, if the pilot and channel signals were sentusing orthogonal spreading codes, the orthogonality of the receivedchannel signal is restored after weighting. The restored orthogonalitysubstantially reduces correlated interference from other trafficchannels that occur as a result of the deorthogonalization due tochannel distortion. The weighted received signal is despread by atraffic despreader 516 using the corresponding traffic code to recoverthe traffic data.

Although the features and elements of the present invention aredescribed in the preferred embodiments in particular combinations, eachfeature or element can be used alone (without the other features andelements of the preferred embodiments) or in various combinations withor without other features and elements of the present invention.

What is claimed is:
 1. A transmitting device comprising: circuitryconfigured to produce a plurality of pilot signals; wherein a differentpilot signal of the plurality of pilot signals is transmitted on each ofa plurality of antennas; wherein each of the pilot signals is derivedfrom a pseudo noise (PN) sequence and a bit sequence of the PN sequencefor each of the pilot signals is different; the circuitry is furtherconfigured to produce a plurality of data streams; wherein each of thedata streams has data bits combined with bits of a PN sequence; and thecircuitry is further configured to weight the data streams in responseto weight information received from a receiving device and transmit theplurality of weighted data streams using the plurality of antennas. 2.The transmitting device of claim 1 wherein the plurality of weighteddata streams are transmitted to the receiving device.
 3. A method foruse by a transmitting device, the method comprising: producing aplurality of pilot signals; wherein a different pilot signal of theplurality of pilot signals is to be transmitted on a respective one of aplurality of antennas; wherein each of the pilot signals is derived froma pseudo noise (PN) sequence and a bit sequence of the PN sequence foreach of the pilot signals is different; producing a plurality of datastreams; wherein bits of each of the data streams has data bits combinedwith bits of a PN sequence; weighing the data streams in response toweight information received from a receiving device; and transmittingthe plurality of pilots signals and the weighted data streams using theplurality of antennas.
 4. The method of claim 3 wherein the plurality ofdata streams are transmitted to the receiving device.
 5. A receivingdevice comprising: circuitry configured to transmit weight informationto a transmitting device for use in weighting a plurality of datastreams; the circuitry is further configured to receive a downlinksignal including a plurality of pilot signals and a plurality of datastreams; wherein a different pilot signal of the plurality of pilotsignals was transmitted from a different antenna of a plurality ofantennas of a transmitting device; wherein each of the pilot signals wasderived from a pseudo noise (PN) sequence and a bit sequence of the PNsequence for each of the pilot signals is different; and the circuitryis further configured to recover data from the plurality of datastreams; wherein each of the data streams has data bits combined withbits of a PN sequence; wherein each of the data streams was weightedbased on the transmitted weight information.